Cathode unit for electric discharge tubes



June 1957 w. A. JURGENS CATEQDE UNIT FOR ELECTRIC DISCHARGE TUBES FiledSept. 16, 1964 INVENTOR.

WILHELMUS A. JURGENS United States Patent 3,327,157 CATHODE UNIT FORELECTRIC DISCHARGE TUBES Wilhelmus Albert Jurgens, Emmasingel,Eindhoven, Netherlands, assignor to North American Philips Company,Inc., New York, N.Y., a corporation of Delaware Filed Sept. 16, 1964,Ser. No. 396,882 Claims priority, application Netherlands, Sept. 20,1963, 298,210 Claims. (Cl. 313278) My invention relates to a cathode foran electric discharge tu'be, and in particular to a directly heatedcathode comprising a plurality of thin wires connected in parallel.

Known constructions of such cathodes comprising parallel thin wiresutilize solid cylindrical supporting rods which, after being mounted inan electrode system, are pulled apart by spring action, resulting in thewire portions being tightened. The cylindrical supports are rods which,prior to incorporation of the cathode in an electrode system, areconnected together solely by the wire portions of the cathode. However,such an assembly does not form a rigid unit which can readily behandled, while all of the wire portions must be connected to thesupporting rods in order to avoid shifting thereof. Moreover, duringmounting in an electrode system, complicated supports and guides for thesupporting rods must be provided to prevent variation in the distance ofthe cathode from the other electrode.

This known construction of a cathode affords the important advantage,however, that the cylindrical supporting rods can adjust themselves sothat all the wires of the cathode are tightened equally, irrespectivelyof small deviations resulting from not particularly accurate mountmg.

US. Patent 3,177,393 discloses a construction for a cathode unit inwhich the cathode wire is wound tightly over two U-shaped supports thesupports being spaced apart by means of a supporting plate as long asthe cathode is not mounted in an electrode system. After mounting, theU-shaped supports are pulled apart by spring action and can somewhatslide over the supporting plate so that the cathode wires invariablyremain tightened. However, when inaccurately mounted in an electrodesystem, the U-shaped supports cannot, due to friction with thesupporting plate, relatively adjust themselves sufiiciently to preventthe cathode wires from being tightened unevenly. However, this priorconstruction affords the advantage that the cathode forms a rigid unitwhich can easily be handled even prior to mounting. The wound cathodewire need only be connected at its ends to one of the supports.

The construction according to the present invention affords theadvantages of the above-mentioned constructions without thedisadvantages thereof. According to the invention, the cylindricalsupporting bodies are hollow cylinders spaced apart by a body which isrod-shaped at least at its ends and passes through a central apertureprovided in each cylindrical envelope.

Since the aperture in the cylindrical envelope is a little larger thanthe cross-section of the rod-shaped portion of this body, thecylindrical supports can adjust themselves with respect to thesupporting rod and mutually, resulting in a uniform tension in the wirebeing obtained even if the mounting is not particularly accurate.Besides, the assembly comprising the cylinders and the body forms, aftertightly winding the cathode wire on it, a rigid unit which can easily behandled. It is to be noted that the sectional area of the cylinders mayhave any arbitrary shape.

As a rule, metallic hollow cylinders will be used which are supported inan insulated manner by a ceramic rod.

However, it is also possible to use hollow cylinders internally coveredwith insulating material, together with a metallic body, or insulatingcylinders on which a metallic strip may be provided for electricallyconnecting the wire portions of the cathode in parallel. If desired, thestrip may be divided into various sections to enable certain groups orall of the parallel cathode wires to be connected in series for a higherheating voltage and a lower heating current to be used. As a furtheralternative, the body may be constituted by either two metal partsseparated by an insulating body, or a plate, made of metal or ofinsulating material having rod-shaped portions which extend into thesupporting cylinders.

The invention will now be described with reference to the accompanyingdrawing, in which:

FIGURE 1 shows a cathode unit after being mounted in a tube;

FIGURE 2 is a side view of the cathode unit of FIG- URE l, but prior tomounting in a tube;

FIGURES 3, 4 and 5 show portions of other em'bodiments according to theinvention.

The cathode unit shown in FIGURES 1 and 2 comprises hollow supportingcylinders 1 and 2 of metal, for example, of nickel. Each of thecylinders 1 and 2 has a central aperture 12 through which extends aninsulating rod 3, which bears against the inner sides of the cylinders 1and 2, thus spacing them apart. A cathode wire 4 covered withelectron-emissive material 5 is wound over the cylinders 1 and 2, theemissive layer 5 being scraped oil the portions of the wire 4 which bearon the cylinders 1 and 2. The unit shown in FIGURE 2 forms a rigidassembly after the ends of the cathode wire are welded to the cylinder 1or 2.

The cylinder 2 is fixed in a mica plate 13 by means of clasps 6, 7 and8, the cylinder 1 being secured to a spring 11 by means of clasps 9 and10. The spring provides for the wire portions of the cathode to remaintightened when the cathode wires expand upon heating.

Since the supporting rod 3 passes through the apertures 12 with someclearance, the cylinder 1 can slightly deviate sidewards and tilt aboutthe supporting rod 3 so that, if the cylinder 2 is mounted inaccurately,the cylinder 1 can adjust itself so that all of the wire portions 4, 5are again tightened evenly.

In the embodiment shown in FIGURE 3, the cylinders 5 are of ceramicmaterial, each having a metallic strip 16 formed or provided on it bychemical or mechanical means to enable the wire portions of the cathodeto be electrically connected in parallel. If desired, the metal strip 16may be subdivided on one or both cylinders so as to obtainseries-connected groups of wire portions connected in parallel. As analternative, all of the parallel wire portions may be electricallyconnected in series.

In the embodiment shown in FIGURE 4, the metal cylinders 1 and 2 arespaced apart by metal rods 17 and 18 which are connected together in aninsulating manner with the aid of a glass or ceramic bead 19.

In the embodiment shown in FIGURE 5, the member is a metal plate 20which spaces apart the cylinders 1 and 2 by means of two ceramicrod-shaped parts 21.

The plate-shaped part 20 forms a separation between the two planes inwhich the cathode wires 4 are located and this is favorable for shortwaves since the electrons of the two planes in which the cathode wiresare located are now separated, resulting in a specific, sharply-definedtransit time of the electrons.

In conjunction with the embodiment of FIGURE 3 the parts 21 may likewisebe of metal and integral with the plate 20, if desired. Since the plate20 becomes fairly hot, it is possible to provide on it a metal having agettering effect at a high temperature, for example, zirconium in thepulverulent state. If desired, a certain potential maybe appliedto theplate in order to improve its'shielding action or geetering action. Asan alternative, the plate may be conductively connected to one of thesupporting cylinders.

The present invention is not limited to the examples described.

What is claimed is:

1. A directly heated cathode for an electric discharge tube comprising apair of spaced hollow cylindrical supports having aligned aperturestherein, a plurality of parallel thin wires wound over the two supports,and a body having a rod-shaped portion extending between and throughsaid apertures into each of said supports for spacing the supports agiven distance apart, said apertures having a diameter larger than thatof the rod.

2. A directly heated cathode for an electric discharge tube comprising apair of spaced hollow cylindrical supports having aligned aperturestherein, a plurality of parallel thin wires wound over the two supports,and a body having a rod-shaped portion extending between and throughsaid apertures into each of said supports for spacing the supports agiven distance apart, said apertures having a larger cross-section thanthat of said rod-shaped body.

3. A directly heated cathode for an electric discharge tube comprising apair of spaced hollow cylindrical supports having aligned aperturestherein, a plurality of parallel thin wires wound over the two supports,and a rodshaped ceramic body extending between and through saidapertures into each of said supports for spacing the supports a givendistance apart, said apertures having a larger cross-section than thatof said rod-shaped body.

4. A directly heated cathode for an electric discharge tube comprising apair of spaced hollow cylindrical supports having aligned aperturestherein, a plurality of parallel thin wires wound over the two supports,and a rod-shaped body extending between and through said apertures intoeach of said supports for spacing the supports a given distance apart,said rod-shaped body comprising two metal portions connected togetherand insulated from each by the interposition of an insulating material,said apertures having a larger cross-section than that of saidrod-shaped body.

5. A directly heated cathode for an electric discharge tube comprising apair of spaced hollow cylindrical supports having aligned aperturestherein, a plurality of parallel thin wires wound over the two supports,and

'a body extending between and through said apertures into each of saidsupports for spacing the supports a given distance apart, said bodycomprising a plate-shaped portion intermediate two rod-shaped portionseach of which extend into one of said apertures, said apertures having alarger cross-section than that of said rod-shaped body.

6. A directly heated cathode for an electric discharge tube comprising apair of spaced hollow cylindrical insulating supports having alignedapertures therein, a plurality of parallel thin wires wound over the twosupports,

each of said supports having a strip of conductive material forconnecting said wires in parallel, and a body having rod-shaped portionsextending between and through said apertures into each of said supportsfor spacing the supports a given distance apart, said apertures having alarger cross-section than that of said body.

7. A directly heated cathode for an electric discharge tube comprising apair of spaced hollow cylindrical supports having aligned aperturestherein, a plurality of parallel thin wires wound over the two supports,a body having rod-shaped portions extending between and through saidapertures into each of said supports for spacing the supports a givendistance apart, and means to connect said body in an electricallyconductive manner to one of said cylindrical supports, said apertureshaving a larger cross-section than that of said body.

8. A directly heated cathode for an electric discharge tube comprising apair of spaced hollow cylindrical supports having aligned aperturestherein, a plurality of parallel thin wires wound over the two supports,and a rod-shaped body covered at least in part with a getter materialextending between and through said apertures into each of said supportsfor spacing the supports a given distance apart, said apertures having alarger crosssection than that of said body.

9. A directly heated cathode for an electric discharge tube comprising apair of spaced hollow cylindrical ceramic supports having alignedapertures therein, a plurality of parallel thin wires wound over the twosupports, each of said supportshaving metallized portions for connectingsaid wires electrically in parallel and a body having rod-shapedportions extending between and through said aperturesinto each of saidsupports for spacing the supports a given distance apart, said apertureshaving a larger cross-section than that of said body.

10. A directly heated cathode for an electric discharge tube comprisinga pair of spaced hollow cylindrical supports having aligned aperturestherein, a plurality of parallel thin wires wound over the two supports,a body having rod-shaped portions extending between and through saidapertures into each of said supports for spacing the supports a givendistance apart, and resilient means engaging said cylindrical supportsfor imparting tension to said wires mounted thereon, said apertureshaving a larger cross-section than that of said body.

References Cited UNITED STATES PATENTS 1,720,442 7/1929 Robinson 3l3-278 1,980,937 11/1934 Dodge 3l3260- 2,656,477 10/1953 Herbold 313-346FOREIGN PATENTS 249,768 5/ 1963 Australia.

JAMES D. KALLAM, Primary Examiner.

JOHN W. HUCKERT, Examiner.

A. 1; JAMES, Assistant Examiner.

1. A DIRECTLY HEATED CATHODE FOR AN ELECTRIC DISCHARGE TUBE COMPRISING APAIR OF SPACED HOLLOW CYLINDRICAL SUPPORTS HAVING ALIGNED APERTURESTHEREIN, A PLURALITY OF PARALLEL THIN WIRES WOUND OVER THE TWO SUPPORTS,AND A BODY HAVING A ROD-SHAPED PORTION EXTENDING BETWEEN AND THROUGHSAID APERTURES INTO EACH OF SAID SUPPORTS FOR SPACING THE SUPPORTS AGIVEN DISTANCE APART, SAID APERTURE HAVING A DIAMETER LARGER THAN THATOF THE ROD.